Flexible tool



April 23, 1963 E. w. DE LANCEY FLEXIBLE TOOL Filed Dec. 3, 1959 3,086,411 Patented Apr. 23, 1963 3,086,411 FLEXIBLE TOOL Eslie W. De Lancey, Martinsville, Va., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Dec. 3, 1959, Ser. No. 857,084 4 Claims. (Cl. 78-1) This invention relates generally to the manufacture of spinnerets of the type which are used in the production of filamentary structures from viscous organic materials and, more particularly, to an improvement in the tools which are used in fabricating the minute extrusion holes in a spinneret.

It is well known that the preparation of conventional spinneret holes involves multiple machining steps such as punching, drilling and broaching, and that various difficulties are encountered in aligning the tools used in successive steps with the work that has already been accomplished. When the tools are aligned perfectly, a pattern of uniform symmetrical holes is obtained. However, when not so aligned, there is always a likelihood that the tool will be damaged or that the resulting holes will be imperfect. These imperfections usually lead to the extrusion of non-uniform filaments.

The most important object of the present invention is to provide a self-aligning punch tool which may be used with otherwise conventional machinery in the fabrication of uniform spinneret holes.

Another important object of the invention is the provision of a flexible link between a punch member and its mounting for the purposes of facilitating proper alignment of the punch member and preventing damage to the tool.

With these and other objects in view, the punch tool of the present invention comprises generally an elongated flexible shank adapted to fit at one end thereof into the chuck of a punch press and having a punch member attached thereto at the opposite end.

Other objectives will become apparent in the following specification wherein reference is made to the accompanying drawings in which:

FIGURE 1 is a. side view of a punch tool made in accordance with the teachings of the present invention and shown in association with a press chuck;

FIG. 2 is an enlarged side view illustrating the failure of a rigidly mounted punch when misaligned with the work;

FIG. 3 is a side view of the punch tool of FIG. 1, showing the initial deformation of the shank when the tool is slightly misaligned;

FIG. 4 is an enlarged side view showing the resultant deformation of the tool;

FIG. 5 is a side view of a punch having a different end configuration;

FIG. 6 illustrates the self-aligning characteristics of the surface punch shown in FIG. 5; and

FIG. 7 is a perspective view of still another end configuration which may be employed.

The terms punch and punch member," as used herein, are intended to encompass the variety of tools which are useful in the fabrication of holes, passages, indentations and the like, and which are similar in their general appearance to a punch of the type which is adapted for attachment to the chuck of a punch press. Where these terms are used, there is no intention of limiting the description or utility of the improvements disclosed herein to a punching step as distinguished from such machining steps as cutting, stamping and the like.

As shown in FIG. 1, the punch tool of the present invention consists of a flexible, elongated cylindrical shank 10 which has a punch member 12 attached thereto by a coupling device 14. Shank 10 is illustrated in conjunction with a punch press chuck 16 within which it is held in place by a set screw 18. The shank is preferably made of spring steel and should have a length to diameter ratio of about 16:1. This ratio may be as low as 8:1 or as high as 30:1.

A fabrication method in which the instant tool has special utility has been disclosed in the copending application of Cobb, Ser. No. 776,585, filed November 26, 1958, now Patent No. 3,017,789 issued January 23, 1962. This method involves the steps of stamping a blank of titanium or the like at the location of each spinneret hole with a punch tool to present a dimple on the reverse surface of the metal blank, grinding off the dimples, and surface punching through the resulting orifices into the holes. Where the punch is slightly misaligned with the hole during the surface punching step of Cobb, the punch member may be sheared off or the hole may be irregular. if the blank is prepared by countersinking and a rigid punch is employed, the difficulties illustrated herein in FIG. 2 may be encountered in the stamping step of Cobb as well as in the surface punching step. The resulting difference in the length of the opposed walls within the hole is apparent from the dimensions a and b in FIG 2. Since the extruded material is subject to different frictional forces, poor filament uniformity results. It is apparent that the beneficial effect of the usual tungsten carbide tip is also lost when the tool is misaligned.

In FIGS. 3 and 4, the stamping step has been illustrated as carried out with a slightly misaligned punch tool that is made in accordance with the teachings of the present invention. In FIG. 3, a misaligned tool has been passed into a countersink 20 of a spinneret blank 22. With this initial condition of misalignment, shank 10 easily deflects and permits the punch 12 to slide down the countersink incline. Before upsetting blank 22, the punch centers itself in the bottom of the countersink. As shown in FIG. 4, blank 22 is positioned on a soft metal back-up plate 24 for the stamping step. When the latter step is completed, shank 10 has assumed the deformed configuration of FIG. 4. Although initially misaligned with the countersink, the balance of forces acting on punch member 12 has realigned the member 12 and the misalignment has been transmitted to the flexible shank 10, as indicated at 13.

According to the Cobb method, after grinding away the dimple 26 shown in FIG. 4, the blank 22 is punched through the hole left by punch member 12. Obviously, the shape of the punches depends on the desired shape of the filament to be extruded through the finished spinneret hole. The punches shown by Cobb are rectangular in cross section. Where the punch used in the stamping step is round (FIGS. 1 and 3), the surface punch will also be round and may be provided with a pilot ball point 40, as illustrated in FIG. 5. Ball point 40 should have a diameter less than that of the punch so as to perform its guiding function and leave a cutting ring 42 which has a width of about 0.0005 inch. The manner in which such a surface punch becomes realigned automatically has been illustrated in FIG. 6.

Another configuration which may be employed in stamping and surface punching irregularly shaped spinneret holes has been illustrated in FIG. 7. The parallel straight wall sections indicated at c in FIG. 7 allow the formation of finite straight Walls in the finished spinneret hole. This cruciform punch is made by machining the punch member as close as possible to the final size in unhardened tool steel or its equivalent. The final size is obtained by pressing the punch member into a shaving die of the desired size and shape. It is then 3 hardened in the conventional manner and sharpened by hand polishing.

The incorporation of a flexible shank with a punch tool having a cruciform, rectangular, Y or other irregular end configuration is advantageous when punching or stamping into a countersink and in carrying out such operations as the surface punching step disclosed by Cobb. In the latter instance, the tool is not self-aligning but may be aligned manually to achieve the same final results shown in FIG. 6. Where the provision of a guiding feature is practicable (FIGS. 5 and 6), the advantages of a self-aligning punch may be realized in the surface punching step as well as in the stamping step.

It is apparent that many changes and modifications may be made in the disclosed punching tool and that it may be used in many operations analogous to those specifically disclosed herein without departing from the spirit of the present invention which is therefore intended to be limited only by the scope of the appended claims.

I claim:

1. A punch tool comprising: a longitudinal inextensible, flexible shank adapted at one end thereof to fit into a chuck; and a punch member attached to the shank at its opposite end.

2. The punch tool of claim 1 wherein said shank is cylindrical, of spring steel, and has a length to diameter ratio not less than 8:1 and not more than 30:1.

References Cited in the file of this patent UNITED STATES PATENTS 873,116 Ashenberg Dec. 10, 1907 999,182 Pettengill July 25, 1911 1,887,085 Ehrlich Nov. 8, 1932 1,938,424 Hart Dec. 5, 1933 1,942,539 Deubel Jan. 9, 1934 2,014,698 Reilly Sept. 17, 1935 2,148,221 Schneider Feb. 21, 1.939 2,287,882 Huff June 30, 1942 2,419,826 Dodelin et al. Apr. 29, 1947 2,709,492 Thomann et a] May 31, 1955 2,863,209 Klopfer Dec. 9, 1958 FOREIGN PATENTS 353,800 France July 8, 1905 

1. A PUNCH TOOL COMPRISING: A LONGITUDINAL INEXTENSIBLE, FLEXIBLE SHANK ADAPTED AT ONE END THEREOF TO FIT INTO A CHUCK; AND A PUNCH MEMBER ATTACHED TO THE SHANK AT ITS OPPOSITE END. 